Apparatus for introducing molten metal into a strand casting mold

ABSTRACT

A nozzle consisting of a pouring tube and a return cup extends down into a strand casting mold for pouring molten metal into it. The return cup is suspended in the mold at the lower end of the pouring tube and is submerged below the liquid level in the mold in a position to receive the metal issuing from the pouring tube and redirect it upwardly along the inside wall of the cup. The cup is dimensioned and located so that the eddies that are formed by the countercurrent flow of metal therein will lose their intensity before reaching the bottom and will die out before reaching the openings in the upper part of the cup through which the upwardly flowing metal escapes into the surrounding mold. The inside of the cup is large enough for its side wall and upper face of its bottom to be free from the eddies, while the outside of the cup is small enough to keep the metal that flows down around the outside of the cup from accelerating. The result is that the molten metal leaving the cup is substantially free of turbulence and flows in such a manner that the objectionable inclusion materials in the metal float up to the top of the molten body of metal in the mold around the cup instead of being carried down into the casting strand to contaminate the product upon solidification.

United States Patent Whisler et a1.

[ 1 Nov. 28, 1972 154] APPARATUS FOR INTRODUCING MOLTEN METAL INTO A STRAND CASTING MOLD [72] Inventors: Howard E. Whisler, Harrison; Bhupendra Umedchand Shah, Canton; Gerald Vernon Jeskey, I-Iartville; Ray Albert Bloom, North Canton, all of Ohio [73] Assignee: The Timken Roller Bearing Company, Canton, Ohio [22] Filed: Oct. 9, 1970 [21] Appl. No.: 79,500

[52] US. Cl ..164/337, 164/281 [51 Int. Cl. ..B22d 37/00 [58] Field of Search ..l64/28l, 283, 335, 337, 256, 164/82, 311, 83, 93, 133, 362, 273; 249/105,

[56] References Cited UNITED STATES PATENTS 3,340,924 9/ l 967 Ludwig 164/281 3,371,704 3/1968 Astrov ..164/281 3,517,726 6/1970 Mills ..l64/281 X 2,290,083 7/ 1942 Webster ..164/337 X 3,587,719 6/1971 Schrewe ..l64/28l FOREIGN PATENTS OR APPLICATIONS 733,705 4/1943 Germany 164/281 Primary Examiner-J. Spencer Overholser Assistant Examiner-John S. Brown AttorneyBrown, Murray, Flick and Peckham [57] ABSTRACT A nozzle consisting of a pouring tube and a return cup extends down into a strand casting mold for pouring molten metal into it. The return cup is suspended in the mold at the lower end of the pouring tube and is submerged below the liquid level in the mold in a position to receive the metal issuing from the pouring tube and redirect it upwardly along the inside wall of the cup. The cup is dimensioned and located so that the eddies that are formed by the countercurrent flow of metal therein will lose their intensity before reaching the bottom and will die out before reaching the openings in the upper part of the cup through which the upwardly flowing metal escapes into the surrounding mold. The inside of the cup is large enough for its side wall and upper face of its bottom to be free from the eddies, while the outside of the cup is small enough to keep the metal that flows down around the outside of the cup from accelerating. The result is that the molten metal leaving the cup is substantially free of turbulence and flows in such a manner that the objectionable inclusion materials in the metal float up to the top of the molten body of metal in the mold around the cup instead of being carried down into the casting strand to contaminate the product upon solidification.

1 Claim, 4 Drawing Figures PATENTED rmv 28 I972 SHEET 1 BF, 2

Fig. 3

ATTORNEYS.

APPARATUS FOR INTRODUCING MOLTEN METAL INTO A STRAND CASTING MOLD The strand casting of metal, by allowing it to issue in a continuous strand from the bottom of a mold, is now well known and in extensive use. Objectionable inclusions resulting from deoxidation and other sources normally are present in variable amounts within the molten metal being cast. The stream of molten metal pouring into a strand casting mold has considerable velocity and therefore causes deep penetration of objectionable inclusion materials entering the strand with no chance to separate from the turbulent metal and so they pass out with it and contaminate the strand. Baffles or cups have been placed beneath the outlets of the pouring tubes in an effort to reduce the velocity of the molten metal, but their design has been such that they have not succeeded very well and they have created another problem; namely, the turbulence they generate results in surface erosion and adds further objectionable inclusion materials to the molten metal.

It is among the objects of this invention to provide means for not only effectively reducing the velocity of molten metal entering a strand casting mold, but also to isolate and minimize the turbulence without causing erosion and to allow objectionable inclusion materials to float up to the top of the molten metal in the mold.

The preferred embodiment of the invention is illustrated in the accompanying drawings, in which FIG. 1 is a vertical section through a strand casting mold in which this invention has been incorporated;

FIG. 2 is a horizontal section taken on the line ll-ll of FIG. 1;

FIG. 3 is a fragmentary vertical section taken on the line lll-lll of FIG. 1 and showing a strand being cast; and

FIG. 4 is an enlarged vertical section through the lower end of the nozzle, illustrating the fluid flow and eddy generation during strand casting.

Referring to the drawings, a strand casting mold l is open at both top and bottom. The opening in the mold is a shape that will produce a continuous body or strand 2 (FIG. 3) of metal of the desired cross sectional shape and size. As the metal leaves this opening it is cooled and solidified in a well-known manner, not shown. During casting, the mold contains an ever-changing'body of molten metal 3 of considerable height and its upper surface is covered with a layer of slag 4 to protect it from oxidation.

Extending down into the mold and preferably through the slag and into the metal body below it is a nozzle. Part of this nozzle is formed from a delivery pipe or pouring tube 5, the upper end of which is connected to the valve-controlled outlet of a tundish 6, ladle, or the like, containing a reservoir of molten metal.

It is a feature of this invention that the stream of metal issuing from the pouring tube enters the center of a return cup 7 that is suspended in the center of the mold and forms the lower part of the nozzle. This cup, made of refractory material, is immersed in the body of metal in the mold and may be supported in any suitable manner. For example, it can be supported from the top of the mold or hung from the pouring tube or, as shown, it can be integral with the lower end of the pouring tube. The side wall of the cup is substantially vertical and its upper part is provided with ports or openings 8 for low velocity escape of metal from the cup into the surrounding mold. These may be a pair or more of uniformly spaced slots, between which solid portions of the cup join it to the lower end of the pouring tube.

As the stream of metal pours into the cup, it first flows downwardly and then spreads out uniformly and flows upwardly along the inner surface of the cup side wall until it can flow out through openings 8, as indicated by the arrows in FIGS. 3 and 4. The inner dimensions are small enough to cause a sharp reversal of flow in the lower part of the cup so that the upwardly or counter currently flowing metal will rub against the downwardly flowing stream and, due to the viscosity of the metal and the eddies generated around the central stream, as indicated in FIG. 4, will materially reduce the velocity of the metal passing through the cup. In other words, reduction in fluid kinetic energy is effected by fluid-on-fluid friction causing eddy generation, and not as in the past by contact of the fluid with the solid surface of the cup.

The outlet openings are located a short distance below the upper surface of the molten metal in the mold, but above the level of intense eddy generation in the cup. The flow out of the cup openings is such that it has a small vertical velocity component. This carries the inclusions up to the slag layer 4 but not with enough force to disrupt the slag. The slag is only about k to 1 inch above the top of openings 8, so that a short flotation path for the objectionable inclusion materials is provided. If the slag level were lower, the flowing metal would be likely to break it up. If it were higher, the objectionable inclusion materials are apt to be carried down into the mold before they can float up to the slag.

The eddies generated in the cup, if allowed to reach its inner surfaces, would scour and erode them and, therefore, not only quickly wear away the cup but also add still more objectionable inclusion materials to the molten metal. To help avoid this, the bottom of the cup is located far enough below the pouring tube to position it below the region in which the eddies are generated. The stream of metal therefore makes a fairly smooth reversal upon itself without scouring the bottom, as shown in FIG. 4. It also is important that the inner diameter of the cup, although relatively small, be enough greater than the inner diameter of the lower end of the pouring tube to space the side wall of the cup away from the eddies. That is, the upward return path of the flow should be outside the location of intense eddy generation. This will result in relatively smooth upward flow of metal along the inside wall of the cup through regions of low intensity eddies to its outlet openings 8, so that the wall will not be eroded appreciably. In other words, these regions of low intensity eddies act as a settling chamber in which the eddies die out during the upward flow of metal to the outlet ports. The cup is deep enough so that turbulent metal in the cup will not escape through its openings into the mold. The openings are of sufficient width and area to be nonrestrictive to the low velocity non-turbulent flow.

Another feature is that the cup is small enough not to restrict the space around it to such an extent that after the metal leaves the cup it would flow downwardly around the cup at an increased velocity that would carry objectionable inclusion materials down along with it and into the strand.

Due to the position, form and relative dimensions of i the return cup, the metal leaving it flows out of the cup openings at a relatively low velocity in a smooth nonturbulent manner. Consequently, flotation of inclusions will occur up around the cup to the slag, which will not be disturbed by the metal flow. The metal strand leaving the bottom of the mold therefore is much freer of undesirable inclusions than heretofore and can be used where metal of high grade is required and for which ordinary strand cast metal is not suitable.

Although the dimensions of the cup will vary with the length and form of the nozzle and the size of the mold, in one successful application where the pouring tube is approximately 22 inches long and has an outlet 1% inches in diameter, the inner diameter of the cup is twice the latter figure, or 3% inches, and the upper surface of the bottom of the cup is between 7 and 7% inches below the pouring tube outlet, a distance that is equal to about twice the diameter of the inside of the cup. The slots or openings 8 in the upper part of the cup are about 2 inches high and 3% inches wide or equal to the inside diameter of the cup. The outside of the cup is square, as shown in FIG. 2, and inches wide. This nozzle is used with a mold having an interior rectangular shape that is 9 inches by 12 inches. The openings in the cup face the sides of the mold with the shorter dimension, as shown in FIG. 2. The strand 2 leaves the mold at the rate of 28 inches per minute and it is high-grade steel substantially free of inclusions, because they float to the upper part of the mold above the level of the cup and remain with the slag.

According to the provisions of the patent statutes, we have explained the principle of our invention and have illustrated and described what we now consider to represent its best embodiment. However, we desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

We claim:

1. In the production of high grade strand cast metal substantially free of inclusions, the combination with a strand casting mold open at top and bottom, of a nozzle formed from a pouring tube and a return cup and extending down into the mold for pouring a stream of molten metal into it, the lower end of the pouring tube being centered in the mold, and the return cup having a substantially vertical side wall and being suspended in the mold at the lower end of the pouring tube in a'position to receive centrally said stream, the cup being small enough to sharply reverse the stream and redirect it upwardly and along the inside wall of the cup, the bottom of the cup being located far enough below the pouring tube to cause fluid-on-fluid friction and generation of eddies thereby between concentric downward and upward flows of metal in the cup in order to reduce the velocity of the upwardly flowing metal, there being openings at the upper part of the cup above the level of turbulence therein for low velocity escape of the upwardly flowing metal laterally from the cup into the surrounding mold, said openings being located below the molten metal level in the mold and positioned to allow the metal leaving them to flow upwardly at an inclination as it flows laterally away from the cup, the distance from the lower end of the pouring tube to the upper surface of the bottom of the cup being at least twice the inner diameter of the cup to space said eddies from the bottom of the cup, the inner diameter of the cup being substantially twice the inner diameter of the lower end of the pouring tube to space said cup side wall from the eddies, and the outside of the cup being small enough in relation to the mold to keep the metal flowing down around the cup from accelerating, whereby the metal leaving the cup will flow therefrom in such a manner that objectionable inclusion materials in the metal can float up to the top of the molten body of metal in the mold around the cup and be retained by a layer of slag on said body. 

1. In the production of high grade strand cast metal substantially free of inclusions, the combination with a strand casting mold open at top and bottom, of a nozzle formed from a pouring tube and a return cup and extending down into the mold for pouring a stream of molten metal into it, the lower end of the pouring tube being centered in the mold, and the return cup having a substantially vertical side wall and being suspended in the mold at the lower end of the pouring tube in a position to receive centrally said stream, the cup being small enough to sharply reverse the stream and redirect it upwardly and along the inside wall of the cup, the bottom of the cup being located far enough below the pouring tube to cause fluid-on-fluid friction and generation of eddies thereby between concentric downward and upward flows of metal in the cup in order to reduce the velocity of the upwardly flowing metal, there being openings at the uPper part of the cup above the level of turbulence therein for low velocity escape of the upwardly flowing metal laterally from the cup into the surrounding mold, said openings being located below the molten metal level in the mold and positioned to allow the metal leaving them to flow upwardly at an inclination as it flows laterally away from the cup, the distance from the lower end of the pouring tube to the upper surface of the bottom of the cup being at least twice the inner diameter of the cup to space said eddies from the bottom of the cup, the inner diameter of the cup being substantially twice the inner diameter of the lower end of the pouring tube to space said cup side wall from the eddies, and the outside of the cup being small enough in relation to the mold to keep the metal flowing down around the cup from accelerating, whereby the metal leaving the cup will flow therefrom in such a manner that objectionable inclusion materials in the metal can float up to the top of the molten body of metal in the mold around the cup and be retained by a layer of slag on said body. 